Pump Unit For Water Jet Surgery

ABSTRACT

The pump unit according to the invention encompasses at least two piston pumps, which include pump cylinders and pump pistons. Each piston pump comprises at least one inlet valve and an outlet valve. At least the inlet valves, but optionally also the outlet valves, are embodied as springless ball check valves, in the case of which the valve ball is located in an interior, which is defined by a surface of the housing (preferably of the first housing part  11 ) at least on one side. With this design, the actual check valve is only joined and is thus produced completely only when the housing parts are brought together. Check valves, which can be sterilized well and which can be cleaned without any residue, can thus be integrated into the pump unit in a simple and reliable manner.

RELATED APPLICATION(S)

This application claims the benefit of European Patent Application No. 12185019.2 filed Sep. 19, 2012, the contents of which are incorporated herein by reference as if fully rewritten herein.

TECHNICAL FIELD

The invention relates to a pump unit, which is provided in particular for water jet surgery.

BACKGROUND

Water jet surgery is based on the application of a jet of physiological saline solution to a biological tissue, which is severed and/or dissolved completely or partially through this. Depending on process control, tissue sections can be cut by means of surgical interventions using water jets, for example, and parenchymal tissue can be dissolved by protecting the vascular system, or the interstitium. Surgeries, which protect the nerves, for example, are possible with this.

To generate a corresponding water jet, the treatment fluid, in particular NaCL solution must be provided at a desired pressure and/or at a desired delivery volume, so as to then be applied as jet via a surgical instrument. In the state of the art, a pump unit, as it is illustrated in a sectional view in FIGS. 7 and 8, serves to provide the fluid. The pump unit 10 shown therein is embodied as a disposable pump (that is, as product, which is provided for being used once), which is inserted into a corresponding accommodation of a medical device, if necessary, and which is locked in place with the latter. The pump unit 10 comprises a first housing part 11, comprising two pump cylinders 12, 13, which are arranged so as to be axially parallel to one another. They are embodied as round, tube-like appendages, which extend away from a top part 14. Pump pistons 15, 16, which abut on the inner wall of the pump cylinders 12, 13 so as to form a seal and which are arranged so as to be longitudinally displaceable, are arranged in the pump cylinders 12, 13. Connecting means, for example in the form of revolving grooves or projecting lugs or the like, are arranged on the distal ends of the pump cylinders 12, 13 as well as on the pump pistons 15, 16, so as to lock the pump unit 10 and thus the pump cylinders 12, 13 on the one hand and so as to selectively move the pump pistons 15, 16 back and forth on the other hand.

A second housing part 17, which is fixedly connected to the first housing part 11, belongs to the pump unit 10. As can be seen from FIG. 7, a suction channel 18, which is connected to a fluid supply, e.g. a physiological saline solution, via a hose 19, is embodied in the second housing part 17.

The suction channel 18 extends transversely to the pump cylinders 12, 13 and in each case encompasses a junction 20,21, which leads towards the respective pump cylinder 12, 13. An inlet channel 22, 23 is in each case embodied in the first housing part 11 so as to be approximately aligned with said junctions 20, 21. A chamber 24, which is defined by the two housing parts 11, 17 and in which an inlet valve 25 is located, is fixed between the junction 20 and the inlet channel 22. Provision is also made for a chamber 26, which connects the junction 21 to the inlet channel 23 and in which an inlet valve 27 is located.

As is shown in FIG. 8, the second housing part 17 furthermore encompasses a pressure channel 28, which extends parallel to the suction channel 18 and which empties into a connection 29 on one side of the housing part 17. A pressure line, which leads to a surgical instrument, which ejects a fluid jet for surgically treating a tissue, must be connected to said connection 29.

The pressure channel 28 encompasses junctions 30, 31, which communicate with outlet channels 32, 33. The outlet channels 32, 33 connect the interiors of the pump cylinders 12, 13 to the pressure channel 28 via valves 34, 35.

In the case of the pump unit 10, which is illustrated in FIGS. 7 and 8 and which belongs to the state of the art, the two inlet valves 25, 27 and the valves 34, 35 are embodied so as to be equal among one another. For this purpose, the inlet valve 25 is illustrated in an exemplary manner in FIG. 6 as a representation for all of the valves 25, 27, 34, 35.

The valve 25 is a spring-loaded check valve. It encompasses a bushing 36 as outer housing, which encompasses an end plate 37 on one end, from which a tube-shaped appendage 38 extends. An inner housing 40 is arranged in the space 39, which is enclosed by the appendage 38. Said inner housing 40 is a thin-walled metal part, for example, which is connected to the bushing 36 in a flange 41, which is oriented outwardly, e.g. in a press fit. The inner housing 40 encloses an inner space 42, in which a valve ball 43 is arranged. The latter is located on the edge 44 of a bore 45, which permeates the end plate 37 and thus seals the latter. A pressure spring 46 presses the valve ball 43 against the edge 44, which thus forms a valve body seat. With its end, which faces away from the valve ball 43, the pressure spring 46 is supported on an edge 47 of a distal end of the inner housing 40, which is curved inwardly, e.g. The inner housing 40 furthermore encompasses at least one lateral window 48, which is covered for the most part by the valve ball 43 in FIG. 6 and which serves as outflow opening.

In practice, such pump units have proven themselves on principle. However, the production and handling thereof requires some attention. The pump unit is a sterile medical product. This requires that the used components, for example the valves, already have a defined degree of purity in the production process, which takes place in a clean room. With reference to the valves, which are used in the state of the art, this means that they are free from process materials, such as oils and fats, for example, and free from cleaning agents. In the case of valves, in the case of which a spring means presses the valve ball into the valve body seat, this cleaning process is almost not possible or is possibly only under difficult conditions. This cleaning effort is enormous.

After the production or the assembly, respectively, of the pump unit, a complete sterilization of this pump unit 10 must be ensured. For this purpose, the pump unit can be subjected to a gas sterilization method (e.g. with ethylene oxide). For this purpose, however, the gas must be able to pass through at least one side of the respective valve pairing (outlet/inlet), so that it can penetrate into all of the relevant cavities. In response to the use of springloaded inlet and outlet valves, this ability to pass through is not provided sufficiently.

A further requirement on such a pump unit is the immediately operability or readiness, respectively, after its storage. The shelf life after the sterile production can be up to 3 years here. The inlet valves of pump units, which must be removed from a storage, must already open when applying a small low pressure/vacuum of maximally −350 mbar. Due to the different physical influences, such as jamming or the ball getting stuck in the ball seat, for example, this is not always at hand in the case of the spring-loaded inlet valves, which correspond to the state of the art, which then leads to a malfunction of the pump unit.

This is why pump units 10, in the case of which the pressure springs 46 of the two inlet valves 25, 27 are missing, have thus also been used already. These pump units have proven themselves in practice. The inlet valves did no longer get stuck in the case of these pumps and the permeability for the gas, which is used for the sterilization, is at hand completely. A certain functional impairment, however, is noticeable in the case of these pump units to the effect that the feed line must now be vented completely, so as to be able to ensure the initial filling of the pump. In addition, it turned out that the flow rate is no longer ensured in response to very low effect stages, thus in response to very low piston speeds. In response to low effect stages, the fluid flow conveyed by the pump piston 15, 16 is low and is not sufficient to ensure a correct switching behavior of the valves in the case of the valves, which correspond to the state of the art.

SUMMARY

Based on this, it is the object of the invention to specify a pump unit, which encompasses an improved area of application.

Based on the known pump unit, the pump unit according to the invention is characterized by a special embodiment of at least the inlet valves. They are embodied so as to be springless and without inner housing. The valve closing elements in the form of valve balls are arranged in the interior of the valve so as to be capable of moving freely and are not caught in a separate inner housing. They move loosely and do not abut with a pretension at any location of the interior. Two measures, which relate to the valve ball, can thus be taken. The valve ball can obtain an increased diameter and it can be made of a material comprising a reduced density. An adhesion or bonding of the valve ball to the inner surfaces, in particular to the valve body seat, is eliminated reliably and it is already made significantly easier to take along the valve ball by means of moved air when the liquid is sucked in. This adds to the fact that the pump unit sucks in treatment fluid reliably when it is first used even in response to slow piston movements. Due to the fact that this can also be ensured in the case of very low effect sizes, in the case of which the pump pistons move at an extremely slow speed, the area of application of the pump unit is expanded towards low effect sizes.

The advantages in view of the expansion of the area of application follow from the redesign of at least the check valves, which are used as inlet valves. The inlet valve is closed only in response to the assembly of the housing parts. Preassembled valves, in the interiors of which, which are not highly accessible, foreign matter could be present, are not used as inlet valves. The inlet of contaminations can thus be controlled better. In addition, they can be removed better and thus completely by means of the cleaning process. Cleaning residues, that is, residues of cleaning agents, which are introduced into the valve in response to the cleaning process of common preassembled valves, can be reduced or avoided. By defining at least one side of the valve interior by means of the first housing part, it is furthermore excluded reliably that foreign matter in the form of production process residues, such as drawing or lubricating grease, e.g., reach into the interior or remain at that location.

The relationship between ball diameter and valve body seat can be chosen in a different manner than before. The ball can obtain a diameter, which is relatively large as compared to the valve body seat diameter. In the case of a preferred embodiment, the ball diameter is 1.5-times the diameter of the valve body seat. Slightly smaller ball diameters or also larger ball diameters are possible. An adhesion of the ball, that is, a cohesion caused by the tight joining of the ball and of the valve body seat, is avoided with this measure and by omitting a valve closing spring. In addition, the openings and closing of the ball is promoted by the forces of the fluid flow. By omitting the valve housing, more installation space is available for the valve ball. The latter can thus obtain an increased diameter. It thus provides a larger surface for the fluid flow and is thus moved easier in opening as well as in closing direction. This applies in particular for fluid flows comprising very slow flow speeds, thus in response to very low effect sizes.

While the interior, in which the valve ball can move freely, is closed off on least one side, for example a front face, e.g. the front face on the inlet side, from the first housing part, the interior can otherwise be surrounded by surfaces of the second housing part or by a bushing, which is inserted into the housing part. The valve body seat can be embodied on the bushing or also on the second housing part.

This concept also opens up the particularly simple, well-arranged assembly possibility comprising exposed surfaces prior to joining the two housing parts. Sophisticated cleaning standards can be maintained easily with this.

In the case of a preferred embodiment, a housing part encompasses a tube appendage, which projects into a pocket of the other housing part. A pressure-resistant, fluid-tight press fit, which is stressed by the pressure, which prevails in the valve, in a manner, which supports the sealing effect, can be formed with this. In the event that the tube appendage tends to widen when inner pressure prevails, the tube appendage is additionally pressed against the wall of the pocket.

The outlet channel is preferably arranged so as to be located opposite the inlet channel. This results in an inflow, which reliably moves the valve ball in opening or closing direction, even in response to low fluid flow rates. In particular, the interior is free from any particles or mechanical means, except for the valve ball. Flows, which act transversely to the direction of movement of the valve ball, are thus not created anywhere in the interior. An inflow of the valve ball transversely to the flow direction of the medium and transversely to the longitudinal movement of the valve ball is thus avoided. The fluid flow can thus act unhindered, thus optimally on the valve ball and can take the latter along in flow direction, which provides for the precise opening and closing of the valve. Disruptions caused by transverse flows of the medium can be avoided.

Preferably, the outlet of the interior of the valve is surrounded by an opening comprising an edge, which does not match the valve ball, so that the opening cannot be closed by the valve ball. An edge, which does not match the valve ball, is each edge, which does not fit snugly against a ball surface without any gaps. This can thus be an oval opening, a round opening or an opening having any other shape, through which a bar passes, an opening, which is arranged next to an appendage or a pin, or the like. The valve ball can thus not close the outlet, regardless of the prevailing flow speeds and pressures.

Preferably, the interior, in which the valve ball is located, is embodied so as to be substantially cylindrical. The valve ball then defines a ring gap with the cylindrical wall surface. Said ring gap preferably has a cross sectional surface, which is smaller than the cross sectional surface of the inlet. Preferably, the ratio of the cross sectional surface of the ring gap to the cross sectional surface of the inlet is set to be between 0.1 and 1. Preferably, it lies between 0.2 and 0.4—in the case of the concrete embodiment, it is preferably 0.3. The diameter of the valve ball can be, e.g., between 2 mm and 5 mm, preferably 3 mm. It preferably has a small density (e.g. less than 3 g/cm₃). It preferably consists of a plastic or ceramic. It can be a hollow ball.

In a further preferred manner, the two housing parts a reconnected to one another by means of clamping and catch means. The clamping and catch means can do without any adhesives and/or sealants, thus resulting in a design, which is clean and which can be managed in a technologically simple manner.

Further details of advantageous embodiments of the invention are the subject matter of the description, of the drawing or of subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 show an example pump unit according to the invention in different cross sectional illustrations,

FIG. 3 shows an inlet valve of the pump unit according to FIGS. 1 and 2, in schematized enlarged illustrated (not true to scale),

FIG. 4 shows an alternative embodiment of the inlet valve of the pump unit according to the invention in a longitudinal sectional illustration,

FIG. 5 shows the inlet valve according to FIG. 4, in cross sectional illustration,

FIG. 6 shows a valve of a pump unit according to the state of the art, in longitudinally cut illustration, and

FIGS. 7 and 8 shows a pump unit according to the state of the art, in longitudinally cut illustration.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate a pump unit 10, which, except for the design of its inlet valves 25, 27, corresponds to the pump unit 10 according to the state of the art, as it was described above in context with FIGS. 6 to 8. As far as structural and/or functional conformity, the reference numerals introduced in context with FIGS. 6 to 8 are thus used correspondingly in FIGS. 1 to 5. With the exception of the below-described details, the description of the design and of the function provided for FIGS. 6 to 8, in particular for FIGS. 7 and 8, applies accordingly for the embodiments according to the invention: The inlet valves 25, 27 have the same design and are illustrated schematically in FIG. 3 using the example of the inlet valve 25. The description thereof applies accordingly for the inlet valve 27.

As can be seen from FIG. 3, the first housing part 11 encompasses a pocket 49, which starts at a slit 50, in the case of which the first housing part 11 and the second housing part 17 connect to one another. The pocket 49 is embodied cylindrically, for example. A similar pocket 51 is embodied in the second housing part 17 and is arranged such that the two pockets 49, 51 are aligned with one another and form the chamber 24.

A bushing 36 a is pressed into the pocket 51 or is anchored therein in a different manner. This bushing 36 a is made of metal, e.g. It can also consist of other materials, e.g. plastic or ceramic. It includes the bore 45, which serves as inlet channel and which is aligned with the junction 20. On its end, which faces the valve ball 43, the bore 45 expands so as to form a space for accommodating the valve ball 43. The valve body seat 44 is embodied in the transition. A part 38 of the bushing 36 a, which surrounds the interior 39, forms the appendage, which projects into the pocket 49. Preferably, this part of the bushing 36, that is, the appendage 38, is embodied so as to be slightly conical or is provided with ring ribs on the outside (similar to FIG. 6), so as to define a fluid-tight fit with the wall of the pocket 49 of the first housing part 11.

On its side 52, which connects to the inlet channel 22, the interior 39 is thus defined by a surface of the first housing part 11. In addition, it is defined by the inner wall of the bushing 36 a. In the interior 39, the valve ball 43 is capable of moving freely in a direction of movement, which is suggested by means of a dot and dash line

The diameter of the valve ball 43 is smaller than the diameter of the interior 39. A ring gap 53, which can be seen from FIG. 5, e.g., the cross sectional surface of which is preferably smaller than the cross sectional surface of the bore 45, is defined through this. The cross sectional surface of the ring gap 53 is Pi/4 times the difference from the square of the diameter of the interior 39 and the square of the ball diameter of the valve ball 43. The cross sectional surface of the bore 45 is Pi/4 times the square of the diameter of the bore 45.

The valve body seat formed by the edge 44 is located opposite an outlet opening 54, which is arranged or embodied such that the ball 43 can be placed in front of the outlet opening 54 so as not to close it. The edge of the outlet opening 54 does not fit onto the surface of the valve ball 43. This can be attained, e.g. by means of arranging the outlet opening 54 eccentrically, as is suggested in FIG. 3. The outlet opening 54 can furthermore deviate from the circular shape, as is shown in FIG. 5. The arrangement and the shape of the outlet opening 54 define the distance, which the valve ball 43 can cover. The contact distance of the valves can be influenced through this. The shorter the distance, which the ball requires for closing the valve body seat, the quicker the valve can be closed, whereby the return flow of the medium can be reduced to a minimum.

FIG. 4 illustrates a modified embodiment of the inlet valve 25. In the case of the latter, a separate bushing 36 a is omitted. Instead, the bushing 36 a is a one-piece part 36, which is seamlessly connected to the second housing part 17, and is thus a part of the second housing part 17 and consists of the same material as the latter. As a result, the tube-shaped appendage 38 is part of the second housing part 17 and preferably extends in a clamping manner, that is, in press fit, into the pocket 49. Apart from that, the above description applies accordingly.

The pump unit 10 according to the invention, which has been described in this respect, works as follows:

The pump unit 10 is inserted into a medical device, in which actuators are present, which couple with the pump pistons 15, 16. The hose 19 is connected, which is connected to a reservoir for the desired liquid, e.g. NaCl solution. In addition, a line, which leads to a surgical instrument comprising a jet ejection nozzle, is furthermore connected to the connection 29. The actuators for the pistons 15, 16, which move in the opposite direction, are then activated. The smooth-running inlet valves 25, 27 thereby in each case release the way in response to the piston return stroke (intake stroke) and they close, when the respective piston 15 or 16 moves in the direction of the inlet valve 25, 27. The ring gap 53 is thereby dimensioned relatively narrow such that the valve ball 43 is also moved in closing direction, when no liquid, but only air, flows through the respective inlet valve 25, 27. Independent from the size of the ring gap 53, the size and the preferably low weight of the valve ball 43 already also contribute to this. Preferably, said valve ball 43 consists of a plastic. It can be embodied as a solid ball or as a hemisphere. It can also consist of other materials, in particular of ceramic. By designing the inlet valve 25 according to at least one of the above-described measures, the suction of fluid is also facilitated and made possible when the respective piston 15 or 16 moves only slowly.

As soon as the liquid, which is sucked in, fills the respective pump cylinder 12, 13, fluid is pumped through the respective outlet valve 34, 35 at the desired speed into the surgical instrument in response to the respective compression stroke. The movement of the pistons 15, 16 can be matched to one another such that it takes place without any interruptions.

The pump unit 10 according to the invention encompasses at least two piston pumps, which include pump cylinders 12, 13, which are round or which are also designed differently. Each piston pump comprises at least one inlet valve 25, 27 and an outlet valve 34, 35. At least the inlet valves 25, 27, but optionally also the outlet valves 34, 36, are embodied as springless ball check valves, in the case of which the valve ball 34 is located in an interior 39, which is defined by a surface of the housing (preferably of the first housing part 11) at least on one side 52.

With this design, the actual check valve is only joined and is thus produced completely only when the housing parts 11, 17 are brought together. Check valves, which can be sterilized well and which can be cleaned without any residue, can thus be integrated into the pump unit 10 in a simple and reliable manner.

LIST OF REFERENCE NUMERALS

-   10 pump unit -   11 first housing part -   12, 13 pump cylinder -   14 top part -   15, 16 pump piston -   17 second housing part -   18 suction channel -   19 hose -   20, 21 junction -   22, 23 inlet channel -   24 chamber -   25 inlet valve -   26 chamber -   27 inlet valve -   28 pressure channel -   29 connection -   30, 31 junction -   32, 33 outlet channels -   34, 35 outlet valves -   36, 36 a bushing, part -   37 end plate -   38 appendage, part -   39 interior -   40 inner housing -   41 flange -   42 interior -   43 valve ball -   44 edge, valve body seat -   45 bore, inlet channel -   46 pressure spring -   47 edge -   48 window -   49 pocket -   50 slit -   51 pocket -   52 side -   53 ring gap -   54 outlet opening 

1. A pump unit (10) comprising: a pump housing, which encompasses a first housing part (11) and a second housing part (17), wherein the first housing part (11) encompasses at least two pump cylinders (12, 13), which are equipped to accommodate pump pistons (15, 16), wherein the second housing part (17) encompasses a suction channel (18) and a pressure channel (28), wherein inlet valves (25, 27) are active between the pump cylinders (12, 13) and the suction channel (18) and outlet valves (34, 35) are active between the pump cylinders (12, 13) and the pressure channel (28), wherein each inlet valve (25, 27) encompasses an interior (39), in which a valve ball (43) is arranged, wherein the interior (39) encompasses an inlet channel (45) and an outlet opening (54) and is defined by one of the housing parts (11, 17) at least at one location (52) and by a different part (36, 38) at a different location, and wherein the valve ball (43) is supported so as to be capable of moving freely in the interior (39).
 2. The pump unit according to claim 1, wherein the different part (38) is the second housing part (17) or a bushing part (36), which is located in the second housing part (17).
 3. The pump unit according to claim 2, wherein the inlet channel (45) is arranged on the second housing part (17) or on the bushing part (36) and forms the valve body seat (44).
 4. The pump unit according to claim 3, wherein the second housing part (17) or the bushing part (36) forms an appendage (38), which projects into a pocket (49) of the first housing part (11).
 5. The pump unit according to claim 4, wherein the appendage (38) and the first housing part (11) form a fluid-tight press fit.
 6. The pump unit according to claim 1, wherein the outlet is formed by a single opening (54), which is arranged dimactrally opposite the inlet channel (45) relative to the valve ball (43).
 7. The pump unit according to claim 6, wherein the outlet opening (54) is surrounded by an edge, which does not match the valve ball (43).
 8. The pump unit according to claim 1, wherein the interior (39) encompasses a cylindrical wall surface, which defines a ring gap (53) with the valve ball (43).
 9. The pump unit according to claim 8, wherein the ring gap (53) defines a cross sectional surface (Aring) and that the inlet channel (45) defines a cross sectional surface (Ainlet), so that the ratio of the cross sectional surface (Aring) of the ring gap (53) to the cross sectional surface (Ainlet) of the inlet channel (45) is between 0.1 and
 1. 10. The pump unit according to claim 1, wherein provision is made for clamping means and/or catch means for connecting the housing parts (11, 17) to one another. 